Artificial Mouse Babies!?

Yes you read that correctly. A group of scientists at the University of Cambridge have, for the first time ever in March 2017, created an artificial mouse embryo. That is, rather than using the traditional method of mixing an egg and sperm, they have created new life using only stem cells! Even famous cloning experiments such as Dolly the Sheep needed a donated egg cell. The Telegraph hailed this as the dawn of artificial humans, but how true is this? Are we really about to enter the eugenic world from Gattaca*?

“Artificial human life could soon be grown from scratch in the lab, after scientists successfully created a mammal embryo using only stem cells” – Sarah Knapton, The Telegraph

Firstly, let’s review the paper by Harrison et al. that sparked this discussion. To do this we need to set the stage on what exactly causes an embryo to form.

Once the sperm has reached and fertilized the egg, the egg begins to divide multiple times generating a free-floating ball of stem cells. Stem cells are able to turn into any other cell type in the body making them incredible useful in biological research. In this floating ball, three different flavours of stem cells can be found, with each going on to form a different part of the embryo; embryonic stem cells (ESCs) go on to form the body, trophoblast stem cells (TSCs) which form the placenta, and the primitive endoderm stem cells that form the yolk sac which is essential for providing nutrients. From this bundle we get the embryo and eventually the baby mammal.

Previous studies have attempted to create embryo-like structures, using just ESCs, though they have had limited success.

In this study, the authors took cultures of ESCs and TSCs and mixed them together before putting them on a 3D scaffold which gives them a frame on which to grow. The resulting structure very closely resembled a natural embryo. Professor Zernicka-Goetz, one of the authors of this paper wrote “We knew that interactions between the different types of stem cell are important for development, but the striking thing that our new work illustrates is that this is a real partnership – these cells truly guide each other”, highlighting the fact their work showed a remarkable degree of communication between the cell types. This communication was seen via genetically modifying each cell line to fluoresce a different colour (Figure 1). At the end of the experiment, the mixture of cells had separated into a highly polarised, or segregated formation.

Mouse

Figure 1 – An overview of the experiment, notice how at the end the cells are highly organised and segregated. Source.

The authors then compared their artificial embryo to a cultured one and found just how closely they resemble each other (Figure 2). The authors noted that around days 4-5 of the experiment, both embryos were showing signs that the tissues were beginning to form, further showing just how successful this experiment was. However, though they strongly resembled each other, the artificial embryo was very unlikely to develop further, due to the absence of that 3rd type of cell we mentioned earlier – the one responsible for producing the yolk sac.

embryodevelpoment

Figure 2 – A comparison of “natural” embryos and the “artificial” ones. Notice how similar they are, with the same structures in the same locations at around the same time. Source.

Herein lies the big issue. One highlighted by Professor Zernicka-Goetz herself, as she said “We think that it will be possible to mimic a lot of the developmental events occurring before 14 days using human embryonic and extra-embryonic stem cells using a similar approach to our technique using mouse stem cells”. The fear being that using this method one can create “artificial humans”.

This is not true, a fact NHS Choices agrees with, as mouse cells are very different biologically to human cells, and the fact certain components of an embryo were left out in this case – remember the missing yolk sac? It’s also important to note here that the UK has very strict regulation of human embryos with none being allowed to develop past 14 days.

However, this study does has the potential to change the field of embryo research. Currently the one limiting factor is the shortage of embryos, as currently they are sourced from donated eggs at IVF clinics. If this method described by the authors can be adapted for humans, then it might allow for a huge surge of research into developmental diseases in humans, as we would have the resources to do so. Embryo like structures could be made as needed, rather than having to be sourced from a very limited supply. In addition in may be easier to modify these artificial embryos allowing for in depth research during very early embryo development.

In my opinion, I found this paper fascinating, the fact that someone has almost rewritten part of essential biology is just mind blowing. I also agree with the comments made by the authors and others than this study is very unlikely to lead to fully grown mice, let alone fully grown humans, if only due to experimental design. I think that the evidence presented shows that this is very very early work that is a long way from even touching on the fears of those whom believe that artificial humans are on the horizon. I believe that this study may indeed change how embryo research is conducted, and in the best of ways.

If you enjoyed this, you might consider from further reading:

*I highly recommend this film for anyone at all interesting in how genetics might shape the future

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